1. Field of the Invention
The present invention relates to a classifier for separating particulate matter into coarse and fine particles.
2. Description of Relevant Art
Known forms of various classifiers include classifying screens which are of a flat construction. The prior classifiers have been unsatisfactory in that the flat screen provides a relatively small effective screening area and hence a poor handling capacity, and has a small degree of mechanical strength and rigidity. With insufficient rigidity, the screen tends to flex during operation and is unable to classify particles with high precision. An impeller for drawing fine particles is disposed behind the screen and can be a source of contamination when fine particles, having passed through the screen, are deposited on the impeller. The particulate deposits cause the impeller to be eroded and corroded, and act as localized or unbalanced weights to vibrate the impeller while the latter is rotating.